The invention relates generally to amorphous magnetic alloys. More particularly, the invention relates to amorphous magnetic alloys with high saturation magnetization and good thermal stability. The invention further relates to a magnetic component using such alloys and methods for making the magnetic component.
Development of amorphous soft magnetic materials is important to the development of high performance power electronic devices. Amorphous magnetic materials used for applications such as a core of a transformer, an inductor, etc., are typically an iron-based or cobalt-based amorphous alloy (also referred to as metallic glasses). Typically, cores for electric devices are arranged to form a stack or a coil. These stacks or coils are then cut into desired shapes to be employed in the core.
Conventional metallic glasses include Fe—P—C-based metallic glasses first produced in the 1960s, (Fe, Co, Ni)—P—B-based alloy, (Fe, Co, Ni)—Si—B-based alloy, (Fe, Co, Ni)—(Zr, Hf, Nb)-based alloy, and (Fe, Co, Ni)—(Zr, Hf, Nb)—B-based alloy, produced in the 1970s. Most of these alloys are typically subjected to a rapid solidification process, that is, cooling the molten alloy at a sufficient cooling rate to a temperature below a glass transition temperature to suppress crystallization and produce an amorphous alloy. Amorphous alloys generally are prepared with small dimensions. However, the currently employed processes, such as melt spinning, often are subject to process limitations that prevent producing articles with desired dimensions.
The amorphous magnetic alloys exhibit a glass transition at a temperature below a crystallization temperature, with a supercooled liquid region defined as the temperature range between the glass transition temperature and the crystallization temperature. The supercooled liquid region is generally considered to be related to the stability of amorphous phase. Accordingly, the alloys having a wide supercooled liquid region are considered to be excellent in glass-forming ability, which has been further related to good thermal stability of the amorphous phase. Glass-forming ability is required to produce articles with desired shape and dimension from the amorphous magnetic alloy.
U.S. Pat. No. 7,223,310 and U.S. Pat. No. 7,357,844 disclosed a soft magnetic Fe—B—Si-based metallic glass alloy composition exhibiting clear glass transition, wide supercooled liquid region, and having high glass-forming ability and saturation magnetization. However, magnetic properties of such alloys are typically, not stable when the alloys are subjected to thermal processing. Thermal processing may be required to form the alloys into desired geometric shapes.
Thus, there is a need to provide an improved amorphous magnetic alloy having good glass-forming ability and good thermal stability while maintaining the desired balance of magnetic properties. There is a further need for an article having a magnetic component with improved properties as compared to conventional magnetic components. Moreover, there is a need for methods to produce such amorphous magnetic alloys and articles of desired dimensions.